diff --git a/spring-cloud-gateway-mvc/src/test/java/org/springframework/cloud/gateway/mvc/ProductionConfigurationTests.java b/spring-cloud-gateway-mvc/src/test/java/org/springframework/cloud/gateway/mvc/ProductionConfigurationTests.java
index e3054ecc..e2688445 100644
--- a/spring-cloud-gateway-mvc/src/test/java/org/springframework/cloud/gateway/mvc/ProductionConfigurationTests.java
+++ b/spring-cloud-gateway-mvc/src/test/java/org/springframework/cloud/gateway/mvc/ProductionConfigurationTests.java
@@ -44,6 +44,7 @@ import org.springframework.http.RequestEntity;
 import org.springframework.http.ResponseEntity;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
@@ -230,7 +231,20 @@ public class ProductionConfigurationTests {
                         .isEqualTo("host=localhost;foobar");
     }
 
-    @SpringBootApplication
+	@Test
+	@SuppressWarnings({"Duplicates", "unchecked"})
+	public void headers() throws Exception {
+		Map<String, List<String>> headers = rest.exchange(RequestEntity.get(rest.getRestTemplate().getUriTemplateHandler()
+				.expand("/proxy/headers")).header("foo", "bar").header("abc", "xyz").build(), Map.class).getBody();
+		assertThat(headers).doesNotContainKey("foo")
+				.doesNotContainKey("hello")
+				.containsKeys("bar", "abc");
+
+		assertThat(headers.get("bar")).containsOnly("hello");
+		assertThat(headers.get("abc")).containsOnly("123");
+	}
+
+	@SpringBootApplication
     static class TestApplication {
 
         @RestController
@@ -359,6 +373,17 @@ public class ProductionConfigurationTests {
                 proxy.forward(path);
             }
 
+			@GetMapping("/proxy/headers")
+			@SuppressWarnings("Duplicates")
+			public ResponseEntity<Map<String, List<String>>> headers(ProxyExchange<Map<String, List<String>>> proxy) {
+				proxy.sensitive("foo");
+				proxy.sensitive("hello");
+				proxy.header("bar", "hello");
+				proxy.header("abc", "123");
+				proxy.header("hello", "world");
+				return proxy.uri(home.toString() + "/headers").get();
+			}
+
             private <T> ResponseEntity<T> first(ResponseEntity<List<T>> response) {
                 return ResponseEntity.status(response.getStatusCode())
                         .headers(response.getHeaders())
@@ -397,6 +422,10 @@ public class ProductionConfigurationTests {
                 return Arrays.asList(new Bar(custom + foos.iterator().next().getName()));
             }
 
+			@GetMapping("/headers")
+			public Map<String, List<String>> headers(@RequestHeader HttpHeaders headers) {
+				return new LinkedMultiValueMap<>(headers);
+			}
         }
 
         @JsonIgnoreProperties(ignoreUnknown = true)
diff --git a/spring-cloud-gateway-webflux/src/main/java/org/springframework/cloud/gateway/webflux/ProxyExchange.java b/spring-cloud-gateway-webflux/src/main/java/org/springframework/cloud/gateway/webflux/ProxyExchange.java
index 08f44228..a59812ca 100644
--- a/spring-cloud-gateway-webflux/src/main/java/org/springframework/cloud/gateway/webflux/ProxyExchange.java
+++ b/spring-cloud-gateway-webflux/src/main/java/org/springframework/cloud/gateway/webflux/ProxyExchange.java
@@ -350,8 +350,10 @@ public class ProxyExchange<T> {
 	}
 
 	private void addHeaders(HttpHeaders headers, HttpHeaders toAdd) {
-		Set<String> filteredHeaders = filterHeaderKeys(toAdd);
-		filteredHeaders.stream().forEach(header -> headers.addAll(header, toAdd.get(header)));
+		Set<String> filteredKeys = filterHeaderKeys(toAdd);
+		filteredKeys.stream()
+				.filter(key -> !headers.containsKey(key))
+				.forEach(header -> headers.addAll(header, toAdd.get(header)));
 	}
 
 	private Set<String> filterHeaderKeys(HttpHeaders headers) {
diff --git a/spring-cloud-gateway-webflux/src/test/java/org/springframework/cloud/gateway/webflux/ProductionConfigurationTests.java b/spring-cloud-gateway-webflux/src/test/java/org/springframework/cloud/gateway/webflux/ProductionConfigurationTests.java
index f250e993..f2cf0746 100644
--- a/spring-cloud-gateway-webflux/src/test/java/org/springframework/cloud/gateway/webflux/ProductionConfigurationTests.java
+++ b/spring-cloud-gateway-webflux/src/test/java/org/springframework/cloud/gateway/webflux/ProductionConfigurationTests.java
@@ -178,13 +178,16 @@ public class ProductionConfigurationTests {
 	}
 
 	@Test
+	@SuppressWarnings({"Duplicates", "unchecked"})
 	public void headers() throws Exception {
 		Map<String, List<String>> headers = rest.exchange(RequestEntity.get(rest.getRestTemplate().getUriTemplateHandler()
 				.expand("/proxy/headers")).header("foo", "bar").header("abc", "xyz").build(), Map.class).getBody();
-		assertTrue(!headers.containsKey("foo"));
-		assertTrue(!headers.containsKey("hello"));
-		assertEquals("hello", headers.get("bar"));
-		assertEquals("123", headers.get("abc"));
+		assertThat(headers).doesNotContainKey("foo")
+				.doesNotContainKey("hello")
+				.containsKeys("bar", "abc");
+
+		assertThat(headers.get("bar")).containsOnly("hello");
+		assertThat(headers.get("abc")).containsOnly("123");
 	}
 
 	@SpringBootApplication
@@ -282,14 +285,13 @@ public class ProductionConfigurationTests {
 			}
 
 			@GetMapping("/proxy/headers")
-			public Mono<ResponseEntity<Map<String, String>>> headers(ProxyExchange<Map<String, String>> proxy) {
+			public Mono<ResponseEntity<Map<String, List<String>>>> headers(ProxyExchange<Map<String, List<String>>> proxy) {
 				proxy.sensitive("foo");
 				proxy.sensitive("hello");
 				proxy.header("bar", "hello");
 				proxy.header("abc", "123");
 				proxy.header("hello", "world");
 				return proxy.uri(home.toString() + "/headers").get();
-
 			}
 
 			private <T> ResponseEntity<T> first(ResponseEntity<List<T>> response) {
@@ -332,8 +334,8 @@ public class ProductionConfigurationTests {
 			}
 
 			@GetMapping("/headers")
-			public Map<String, String> headers(@RequestHeader HttpHeaders headers) {
-				return headers.toSingleValueMap();
+			public Map<String, List<String>> headers(@RequestHeader HttpHeaders headers) {
+				return headers;
 			}
 
 		}